When materials are put under the condition of high temperature (e.g. 400-1400° C.) for a long time and is required to have excellent strength and long life, one of simple and feasible methods is to apply a protective coating layer on the surface of the material. For example, a protective coating layer for the various metal substrates to be hot-rolled must be a high-temperature resistant coating layer, and further a binder must be added into the coating layer raw materials to effectively bond the coating layer to the material surface. In addition, it is essential that a high-temperature resistant binder is used in many high-temperature resistant materials such as the patching material for high temperature kilns, the refractory material, or the like.
The high temperature resistant property of the binder is one of important factors which affect the protective effect of the coating layer and the strength of the high-temperature resistant material. Generally, such binders that are commonly used may be divided into an organic binder and an inorganic binder. Among them, the organic binder has a limitation of the heating temperature which is lower than 1,400° C.; on the other hand, the inorganic binder conventionally used includes soluble glass and aluminium dihydrogen phosphate. The sodium or potassium in the soluble glass has a strong corrosive effect on the metal substrate at high temperature, and moreover the soluble glass begins to decompose badly at the temperature of above 900° C., thus gradually losing its bonding function. Additionally, because the commonly used aluminium dihydrogen phosphate or the inorganic binder using the same as its main component has very strong acidity, it may severely react with the coating layer or the other components in the material to produce precipitation and thus lower the bonding function, resulting in, for example, uneven coating on the substrate surface of the material, and furthermore the coating layer is easy to crack at high temperature, especially decomposes strongly at the temperature of up to 1,200° C.
By improving the protective effect of the high-temperature resistant coating layer and the bonding strength of the high-temperature resistant material, it is beneficial to reduce the oxidation loss of the hot-rolled metal workpiece during heat treatment in the heating furnace and enhance the stability of the quality of the metal workpiece surface, as well as to increase the strength of the patching material for high temperature kiln or refractory material and extend its service life. To solve the problem regarding the stability of the binder under high temperature, many current methods include adding some high-temperature resistant auxiliary agents such as special material of silicon carbides, but this would increase the binder cost, thus limiting its application range.